Cellulose carboxylic ester silver halide emulsions sensitized with benzothiazole and benzoselenazole quaternary salts



Patented Dec. 6, 1949 UNITED STATES PATENT OFF-ICE Burt H. Carroll andWilliam West, Rochester, N. Y., assignors to Eastman Kodak Company,Rochester, N. Y., a corporation of New Jersey No Drawing. ApplicationJanuary 13, 1948, Serial No. 2,126

This invention relates to sensitized photographic emulsions and moreparticularly to cellulose carboxylic ester silver halide photographicemulsions sensitized with benzothiazole and benzoselenazole quaternarysalts.

It is known that benzothiazole, benzoselenazole, benzoxazole,napthothiazole, simple thiazole and thiazoline quaternary salts whenincorporated in gelatino-silver-halide emulsions for example in aconcentration of from 2 to 8 mg. per 100 cc. of emulsion, act asantifoggants for the emulsions. (See United States Patent 2,131,038,dated September 27, 1938.) It is also known that pyridinium andquinolinium quaternary salts act to supersensitize cyanine dyes inphotographic silver halide emulsions. (See United States Patent2,334,864, dated November 23, 1943.) It is also known that surfaceactive quaternary ammonium salts sensitize photographic silver halideemulsions. (See United States Patent 2,271,623, dated February 3, 1942.)

We have now found that substantially non- I surface. active quaternarysalts of the benzothiazole and benzoselenazole series sensitizecellulose carboxylic ester silver halide emulsions, although these samequaternary salts act as antifoggants in gelatino-silver-halideemulsions. Moreover, we have found that substantially nonsurface activequaternary salts of simple thiazoles, napthothiazoles andtetrahydrobenzothiazoles do not sensitize cellulose carboxylic estersilver halide emulsions.

It is an object of our invention, therefore, to provide sensitizedcellulose carboxylic ester silver halide emulsions. A further object isto provide a process for preparing such emulsions. Other objects willbecome apparent hereinafter.

The quaternary salts which we employ in practicing our invention aresubstantially colorless,

substantially non-surface active quaternary salts of the benzothiazoleand of the benzoselenazole series, which are devoid of nitro groups. Apre fered group of these quaternary salts are represented by thefollowing general formula:

wherein D represents an o-arylene group of the benzene series containingfrom 6 to 8 carbon atoms and which is devoid of nitro groups, e. g. theo-phenylene group, a chloro-o-phenylene v n-propylmercapto,n-butylmercapto,

13 Claims. (Cl. 957) group, a methyl-o-phenylene group, amethoxyo-phenylene group, a bromo-o-phenylene group, anethoXy-o-phenylene group, an ethyl-o-phenylene group, adimethyl-o-phenylene group, etc., Q represents a sulfur atom or aselenium atom, R represents a primary alkyl group containing from 1 to 4carbon atoms, 1. e. methyl, ethyl, n-propyl, isobutyl and n-butyl, aprimary alkenyl group containing from 3 to 4 carbon atoms, 1. e. allyl,2-butenyl and 3-butenyl, a. primary hy-, droxyalkyl group containingfrom 2 to 4 carbon atoms, i. e. B-hydroxyethyl, Y-hydroxypropyl, chydroxypropyl, 5 hydroxybutyl, 'y hydroxybutyl and fi-hydroxybutyl, aprimary alkoxyalkyl group, containing from 3 to 4 carbon atoms, e. g.,B-methoxyethyl, ,s-ethoxyethyl, B-methoxypropyl and Y-methoxypropyl, R1represents a hydrogen atom, a methyl group, an ethyl group, analkylmercapto group containing from 1 to 4 carbon atoms, e. g.methylmercapto, ethylmercapto,

isobutylmercapto, an arylmercapto group containing from 6 to 8 carbonatoms and devoid of nitro groups, e. g. phenylmercapto, p-tolylmercapto,p chlorophenylmercapto, etc., a primary amino group (i. e. -NH2), analkylamino group containing from 1 to 4 carbon atoms, e. g. methylamino,ethylamino, n-propylamino, n-butylamino, etc., a dialkylamino groupcontaining from 2 to 4 carbon atoms, e. g. dimethylamino, diethylamino,etc., an arylamino group containing from 6 to 8 carbon atoms and devoidof nitro groups, e. g. phenylamino, B-tolylamino, pchlorophenylamino,p-methoxyphenylamino, N-methyl- N-phenylamino, etc., or an aralkylaminogroup containing from 6 to 8 carbon atoms, and devoid of nitro groups,e. g. N-methyl-N-benzylamino, benzylamino, p-phenylethylamino, etc., andX :represents an anion, e. g. chloride, bromide,

iodide, methylsulfate, ethylsulfate, p-toluenesulinnate;benzen'esulfonate, perchlorate, acetate,

pr'opionate, n-butyrate, thiocyanate, sulfamate, etc

" Examples of the aboveformulated quaternary '..salts which areespecially useful are: benzothiazole ethiodide, benzothiazolemetho-p-toluenesulfonate, Z-methylbenzothiazole metho-=p-tolu-'ene-sulfonate, 2 -methylbenzothiazole etho-ptoluenesulfonate,2-methylbenzothiazole alliodide, 2 methylbenzothiazole n butiodide, 5-chloro-2-methylbenzothiazole etho--p-toluenesulfonate,2-methylmercaptobenzothiazole metho-ptoluenesulfonate,2-phenylmercaptobenzothiazolej ethiodide, 2-anilinobenzothiazoleethiodide, 2-

The speed increase may be accompanied by a loss in contrast. In the caseof cellulose carboxylic ester silver halide emulsions which areoptically sensitized by the addition of a sensitizing dye, the increasein speed is approximately the same in the color-sensitized andnon-color-sensitized regions of spectral sensitivity. Benzothiazolemethiodide or metho-p-toluenesulfonate effect a large speed increase,but with a considerable lowering of contrast. Z-methylbenzothiazoleetho-p-toluenesulfonate is very active in increasing speed, with I outreducing contrast as much as the unsubstituted benzothiazole quaternarysalt. Z-methylmercaptobenzothiazole metho-p-toluenesulfonateand2-phenylmercaptobenzothiazole ethiodide are very active.

To sensitize cellulose carboxylic ester silver halide emulsions withthese quaternary salts, it is only necessary to disperse the quaternarysalts inthe emulsion. It is convenient'to add the quaternary salts tothe emulsions from solutions in appropriate solvents. Water, methylalcohol or ethyl alcohol or mixtures of these three solvents aresuitable. The concentration of the quaternary salts in the emulsion canvary widely. Usually the optimum sensitizing eifect is obtained at from0.01 to 0.05 gram per liter of emulsion. However, higher or lowerconcentrations can be used. The quaternary salts con be addedto theemulsion at any stage of its preparation, but are most advantageouslyadded to the. finished emulsions just vprior to coating the for thequaternary salts. The concentration of the sensitizing dye can varywidely, e. g. from 5 to 100 mg. per liter of emulsion. Ordinarily from10 to 50 mg. of dye perliter of emulsion sufiices to produce optimumoptical sensitization. Both the sensitizing dyes and the quaternarysalts should be thoroughly dispersed throughout the emulsions bystirring or other means.

Aseellulose carboxylic ester silver halide emulvsions those described inUnited States Patent 2,110,491, dated March 8, 1931, in United States:Patent 2,276,322, dated March 17, 1942, and in United States-Patent2,127,573, dated August 23, 1938, .areexamples. Photographic silverhalide emulsions prepared using as vehicle or carrier hydrolyzedcellulose carboxylic esters, such as ;-hydrolyzed cellulose acetate orhydrolyzed cellulose acetate propionate containing from 19 to ,33 percent by weight of acyl groups are especially useful in practicing ourinvention. Those containing 20 to 26 per cent by weight. of acyl groupsare most advantageously employed. Any cellulose compound especiallythosefccntaihifl only carbon, hydrogen, oxygen and amino nitrogen atoms,or ammonium nitrogenatoms, which are soluble in a mixture ofethyl'alcohol and water (containing from to 50 per cent by-volumeofethyl alcohol) to the extent of 10 g.,per 100 g..of solvent can beemployed as the vehicle or carrier for the silver halide. The silverhalides can be silver chloride, silver bromide, silver iodide ormixtures of one or more of these silver halides, for example.

The following table illustrates results which can be obtained inaccordance with our invention. The emulsionemployed was a hydrolyzedcellulose acetate silver chlorobromoiodide emulsion in which thecellulose acetate contained from 23 to 24 per cent by weight. ofacetylgroups.

Table Speed Gradient Q t Salt 13 ua ems-1W1 1 er 0 v emulsion TotalBlue. Total {335 mm Light Blue 1 Light 1 Light Blue None 3, 610 202 1.O0 1.22 Benzothia'zole'methiodide; 0. 025 5, 890 372 1. 1. 19

None 3 7, 230 2, 880 275 v 1. 54 1. 42 1. 32 Benzothiazole methiodide 0.013 9, 800 4, 680 468 1. 42 1. 05 1. 27 do 0.050 14, 400 5, 600 455 1.041.07 0. 97 Benzothiazolc metho-p-toluen ulfonate. 0.025 10, 200 5, 300478 0. 98 1. 38 1. 21

None 3 2, 950 950 169 1. 41 1.50 1. 36 Z-Methylbenzo-thiazolemetho-p-toluene- O 025 4, 780 1, 480 282 1. 31 1. 38 1. 12

sulfonate. (i) do O. 050 6, 610 1, 940 331 1. 1. 27 1. 12 (j) 2-Methylbenzo-thiazole etho-p-toluene- O. 025 4, 660 1, 660 245 l. 46 1. 48 l.

sulfcnate.

(k) None 3 3,160 1, 200 123 1. 62 1. G2 1.62 (2)"-.. 2l\/Iethyl'mercaptobenzo-thiazole metho- 0 025 4, 160 174 1. 5O l. 58

' ptoluene-sulfonate. (1a)..-. 2-glganylmercaptorbenzothiazolc et l1i0*0 025 7, 230 2, 950 324 1. 84 1. 25 1. 20

l Total ininus-blu e speed' was measured through .a iilter'whichtransmittedsubstantially 110 light of wave length shorter than 500,u. 9 Blue light speed was measuredl through a'filter which transmittedsubstantially no light except between 360 and 500 p 2,3'-dieth'1-4=methyloxathiazolocarbccyzmine iodide used in the emulsion in aconcentration of 20 mg. per

literoi emulsion,. as colorsensitizen. emulsions. One or more of thequaternary salts can be employed.

The quaternary salts can be employed inconjunctionwith sensitizingdyesand the quaternary salts can be added to the emulsion before, after orsimultaneouslywith the sensitizing dyes. One or more sensitizing dyescan be used. The sensitizing dyes can be added to the emulsions in theusual manner from a solution, in an appropriate solvent, e. g. thesolvents'set forth above tizing dyes of these kinds are described anddefined for example .in The Theory of the P110130. graphic Process by C.E. K. Mees, The Macmillan Company, New York, 19.42. erocyanine dyes are.also described by L. G. S.. Brooker in.

15 United States Patent 2,170,803, dated August 29.

1939 and in United States Patent 2,078,233, dated April 27, 1937.Hemicyanine dyes are described by F. L. White and G. H. Keyes in UnitedStates Patent 2,263,749, dated November 25, 1941. Hemioxonol dyes aredescribed by G. H. Keyes in United States Patent 2,186,608, datedJanuary 9, 1940.

The quaternary salts which we employ in practicing our invention for themost part can be prepared from the corresponding benzothiazcle orbenzoselenazole bases by heating the heterocyclic base with theappropriate alkyl salt, using a closed tube where higher temperature aredesired or the volatility of the reactants demands. Methods forpreparing hydroxyalkyl, alkoxyalkyl and other substituted alkylquaternary salts are described in United States Patents 2,231,658, datedFebruary 11, 1941 and 2,213,238, dated September 3, 1940.Alkylmercaptobenzothiazoles and alkylmercaptobenzoselenazoles can beprepared by alkylating the corresponding mercapto compounds. Theresulting alkylmercapto benzothiazoles and benzoselenazoles can then bequaternarized by heating with an alkyl salt.2-arylmercaptobenzothiazoles can be prepared from 2-chlorobenzothiazoles by treating the 2-chlor0- benzothiazoles with anaryl mercaptan, in the presence of triethylamine (Breaker et al., Jour.Am. Chem. Soc. 63, 3200 (1941)). The arylmercaptobenzothiazoles can thenbe quaternarized by heating with alkyl salts (Brooker et al., supra).2-arylmercaptobenzoselenazoles can be prepared in the same manner.2-chlorobenzoselenazole can be prepared as described by Hasan et a1.Jour. Chem. Soc. (London) 1935, 1762. 2- arylaminobenzothiazolequaternary salts can be prepared by condensing2-phenylmercaptobenzothiazole quaternary salts with a primary aromaticamine or a N-alkyl aromatic amine (Brooker et al., supra). Instead of2-phenylmercaptobenzothiazole quaternary salts,2-ethylmercaptobenzothiazole quaternary salts can be used.2-alky1amino-, 2-dia1kylaminoand 2- aralkylaminobenzothiazole quaternarysalts can be similarly prepared using a primary aliphatic amine, asecondary aliphatic amine or an aralkylamine instead of the aryl amine.2-amino-, 2- methylaminoand 2-anilinobenzoselenazole are described byHasan et al., supra. Starting with 2-ethylmercaptobenzoselenazolequaternary salts, 2-arylamino-2-aralkylaminoand2-alkylaminobenzoselenazole quaternary salts can be pre'- pared asdescribed above for the corresponding benzothiazole compounds.2-aminobenzothiazole quaternary salts can be prepared by adding hydrogenchloride to 3-alky1-2-iminobenzothiazoline. 2 aminobenzoselenazolequaternary salts can be similarly prepared from 3-alkyl-'2-iminobenzoselenazolines (described by Hasan et al., supra). Thechloride anion of any of these quaternary chlorides can be converted tothe bromide or iodide anion by treating an aqueous or methyl or ethylalcoholic solution of the quaternary chloride with an aqueous solutionof potassium bromide or iodide. The quaternary chlorides, bromides oriodides can be converted to quaternary perchlorates by treating a hotalcoholic solution of the quaternary halide with an aqueous solution ofsodium perchlorate. Quaternary iodides can be converted to quaternarychlorides, quaternary acetates or quaternary thiocyanates by heating thequaternary iodide with a suspension of silver chloride, silver acetateor silver thiocyanate in methyl alcohol. Similar conversions ofquaternary iodides to quaternary chlorides can be made by heating thequaternary iodide with silver chloride in a phenol. (See United StatesPatent 2,245,249, dated June 10,

The 2-methlybenzothiazole bases from which 2-methylbenzothiazolequaternary salts can be prepared by heating with an alkyl salt, are forthe most part preparable by the method of Fries et al., Ann 407, 208(1915) in which the appropriate thioacetylaniline is oxidized withalkaline potassium ferricyanide. Thus, p-chlorothioacetanilide gives 6chloro 2 methylbenzothiazole. The thioacetylanilines can be prepared bytreatme the corresponding acetylaniline with phosphorus pentasulfide indry benzene or Xylenes. The acetylanilines can be prepared by the actionof acetic anhydride or acetyl chloride on the corresponding anilinecompound. Several of the 2-methylbenzothiazole bases can also beprepared by reducing bis(o-nitrophenyl)disulfides with zinc dust andacetic acid, acetylating the reduction mixture with acetic anhydride andclosing the ring by heating the resulting mixture. Thebis(o-nitrophenyl)disulfides can be prepared irom the correspondingo-bromonitrobenzenes by heating the o-bromonitrobenzene with sodiumdisulfide in methyl alcohol. Thus, 2-bromo-4- chloronitrobenzene givesbis(5-chloro 2 nitrophenyDdisulfide which, on reduction, acetylation ofthe reduction product and heating gives 2 methyl-6-chlorobenzothiazole.2-methylb'en-' zoselenazole bases can be prepared by reducingbis(o-nitrophenyl) diselenides with zinc dust and acetic acid,acetylating the reaction mixture with acetic anhydride, and closing thering by heating the resulting mixture. The bis(o-nitrophenyl)diselenides can be prepared from the corresponding o-bromonitrobenzenesby heating the o-bromonitrobenzenes with sodium selenide in methylalcohol. See also Clark, J. Chem. Soc. (London), 1928, 2313.

What we claimas our invention and desire to be secured by Letters Patentof the United States is:

1. A photographic silver halide emulsion in which the silver'halide isdispersed in a hydrolyzed cellulose carboxylic ester containing from 19per cent to 33 per cent by weight of acyl groups, said emulsion beingsensitized with at least one quaternary salt selected from the group ofquaternary salts represented by the following general formula: Y

Q 1) o-R,

wherein D represents an o-arylene group of the benzene series containingfrom 6 to 8 carbon atoms and which is devoid of nitro groups, Qrepresents a member selected from the group consisting of a sulfur atomand a selenium atom, R represents a member selected from the groupconsisting of a primary alkyl group containing from 1 to 4 carbon.atoms, a primary alkenyl group containing from 3 to 4 carbon atoms, aprimary hydroxyalkyl group containing from 2 to 4 carbon atoms, and aprimar alkoxyalkyl group containing from 3 to- 4 carbon atoms, R1represents a member selected from-the group consisting of a hydrogenatom, a methyl group, an ethyl group, an alkyl mercapto group containingfrom 1 to 4 carbon atoms, an arylmercapto group containing from 6 to 8carbon atoms and which is devoid of nitro groups, a primary amino group,an

alkyl amino group containing'from 1 to 4 carbon amazes 7 atoms, adialkylamino group containing "from? :to 4 carbon atoms, an arylamlnogroup containing ,from 6 to '3 carbon atoms andwhich 'isdevoid of nitrogroups and an aralkylamino group contain- :ing from 6 .to 8 carbonatomsand which is devoid of nitro groups, and X represents an anion.

'2. A photographic silverhalide emulsion in which the silver halide is:dispersed in a hydrolyzed cellulose carboxylic ester containing from 19per cent'to 33 per cent by weight of acyl groups, said emulsion beingsensitized with at least one quaternary salt selected from the groupconsisting-ofthose quaternary salts represented bya'the followinggeneral formula:

wherein D represents an o-arwlene. grouplof the benzene series,containing .irom 6 to, 8 carbon atoms and which is devoid of nitro.groups, ,3 represents a primary alkyl group containing from 1 to 4carbon atoms, and Xrepresents an anion.

S3. A photographic .silver halide emulsion in which the silver halide isdispersed in a hydrolyzed cellulose acetate containingfromldper cent to33 per cent by weight of acetyl groups, said emulsion :beingsensitizedwithat least one quaternary salt selected fromthe groupconsisting of those quaternary salts represented bythe following generalformula:

o ccrn f /N R X wherein D represents an o-arylene group of the benzeneseries containing'from 6 to 8 carbon atoms and which is devoid of nitrogroups, R represents a primary alkylgroup containing from 1 to 4 carbonatoms, vand")! represents an anion.

4. A photographic silver halide emulsion in which the silver halide isdispersed in a hydrolyzed cellulose acetate containing-from per cent to26 per cent by weightof acetyl groups, said emulsion being sensitizedwith at least one quaternary salt selectedafrom the group consisting ofthose quaternary-salts represented by the following general formula:

lyzed-cellulose carboxylic ester containing from 1 19 per cent to 33 percent by-weight of acyl groups, said emulsion being sensitized with atleast one quaternary salt selected from the group consisting of thosequaternary 'saltsrepresented by the following general formula:

wherein D represents an o-arylene :group of the benzene seriescontainingirom 6 :to 8 carbon atoms and-which is devoid of nitrogroups,-R

represents a primary alkyl group containing 'from 1 to 4 carbon atoms,R1 represents an alkylmercapto group containing from 1 to 4 carbonatoms, and X represents an anion.

-:6. ,A photographic silver halide emulsion in which the silver halideis dispersed in a hydrolyzed cellulose acetate containing from 19 130 33per cent by weight of acetyl groups, said emulsion being sensitized withat least one quaternary salt selected from the group consisting of thosequaternary salts represented by the following general formula:

of those quaternary salts represented by'the 01 til lowing generalformula:

R X wherein D represents an o-arylene group ,of'the benzene seriescontaining from 6 to 8 carbon atoms and which is devoid of nit-r0groups, 13, represents a primary alkyl group containing from 1: todearbon atoms, R1 represents anralkylmercapto groupcontaining from M04carbon atoms and X represents ananion,

8. A photographic silver halide emulsion in which the silver halide isdispersed in a hydrolyzedcellulose acetate containing from 20 to '26percent by weight of acetyl groups, said emulsionbeing senitized with,zemethylbenzothiazole etho-p-toluenesulfonate.

9. A photographic silver halide. emulsion ,in whichthe silver halide isdispersed ina hydrolyzed cellulose acetate containing from 20 .to 26 percent by weight of, acetyl groups, said emulsion being, sensitized with21methylmercaptobenzothiazole metho-p-toluenesulfonate.

'10. A photographic silver halide emulsion in which the silver halide,isdispersed inahydroe lyzed cellulose carboxylicester containingirom 19to 33,per cent by weight of .acylgroups, said emulsion beingsensitizedwithat least one quaternary salt selected from the group consisting ofthose quaternary salts represented by the following general formula:

wherein D representsan o-arylenegroupof the 9 atoms and which is devoidof nitro groups, R represents a primary alkyl group containing from 1 to4 carbon atoms, R1 represents an arylmercapto group containing from 6 to8 carbon atoms and devoid of nitro groups, and X represents an anion.11. A photographic silver halide emulsion in which the silver halide isdispersed in a hydrolyzed cellulose acetate containing from 19 to 33 percent by weight of acetyl groups, said emulsion being sensitized with atleast one quaternary salt selected from the group consisting of thosequaternary salts represented by the following general formula:

s D/ )o-sn,

\N R/ x where in D represents an o-arylene group of the benzene seriescontaining from 6 to 8 carbon atoms and which is devoid of nitro groups,R represents a primary alkyl group containing from 1 to 4 carbon atoms,R1 represents an arylmercapto group containing from 6 to 8 carbon atomsand devoid of nitro groups, and X represents an anion.

12. A photographic silver halide emulsion in which the silver halide isdispersed in a hydrolyzed cellulose acetate containing from 20 per centto 26 per cent by weight of acetyl groups, said emulsion beingsensitized with at least one quaternary salt selected from the groupconsisting of those quaternary salts represented by the followinggeneral formula:

wherein D represents an o-arylene group of the benzene series containingfrom 6 to 8 carbon atoms and which is devoid of nitro groups, Rrepresents a primary alkyl group containing from 1 to 4 carbon atoms, R1represents an arylmercapto group containing from 6 to 8 carbon atoms anddevoid of nitro groups, and X represents an anion.

13. A photographic silver halide emulsion in which the silver halide isdispersed in a hydrolyzed cellulose acetate containing from 20 per centto 26 per cent by weight of acetyl groups, said emulsion beingsensitized with 2-phenylmercaptobenzothiazole ethiodide.

BURT H. CARROLL. WILLIAM WEST.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,110,491 Salo Mar. 8, 19382,131,038 Brooker et a1 Sept. 2'7, 1938 2,271,623 Carroll Feb. 3, 19422,334,864 Carroll et a1 Nov. 23, 1943 FOREIGN PATENTS Number CountryDate 496,049 Great Britain Nov. 21, 1938

